Things I wish I had known before wasting a bunch of diamonds.
Getting to Castle level 30 is great, but most power comes from your best Queue strength. I have been beat by lower level castles that have had more research and building levels done than I had.
My best advice is to keep leveling every building at the same pace.
Specifically the following buildings which have the most impact on your queues.
Faction Statues
Adds to hero attack power, faction HP, and march sizes.
Forge:
Adds to Gear attack and gear HP
Barracks:
Unlocks troop levels
Training Grounds
Gotta have more troops, although just upgrade 1 to max level and leave the others for later
TalonNine